IMPRESSION SHEET ASSEMBLY

Abstract: An impression sheet assembly is proposed to enable the pressure exerted on a plane to be determined accurately in a simple manner. This assembly comprises a transparent sheet (1) which is located on the outside and on which the pressure of varying magnitude has to be exerted. The transparent sheet (1) is provided with an adhesive layer (2) on the inside. A component (4) which releases dye and when put under pressure enters into a reaction with the adhesive layer (2) of the transparent sheet (1) is arranged beneath said adhesive layer (2). There is a carrier sheet (6) beneath the dye-releasing component (4). After the image of the pressure distribution has been produced on the adhesive layer (2) and the dye-releasing component (4) has been removed, the adhesive layer (2) is joined to the carrier sheet (6). By providing the carrier sheet (6) with a grid pattern (7) or the like, it is possible, with the aid of a comparison with, for example, a calibration chart (11), accurately to determine the pressure in a specific position from the coloration.

Description: Impression sheet assembly The invention relates to an impression sheet assembly compris¬ ing, from one side, successively, at least a sheet which is located on the outside and is provided with an adhesive layer, a separating sheet, a dye- releasing sheet and a carrier sheet. A device of this type is disclosed in German Patent DE-C2- 3 t 711.539- It is frequently desirable to know the distribution of the pres¬ sure exerted by one article on another article. Footprints or handprints can be considered in this context. One example thereof is the pressure distribution over the underside of a foot. Diabetes patients have a dimin¬ ished sensitivity in, inter alia, the underside of the foot and also have reduced circulation of the blood in this area. The consequence of the lat¬ ter is that the tissue is less able to withstand load, leading to the tis- sue becoming necrotic. Because diabetes patients have a diminished sensi- - tivity to overstraining, this is not noticed. It is therefore important that when designing, for example, orthotic devices, the pressure distribu¬ tion over the underside of the foot can be accurately recorded and the shape of the insole can be adapted to this pressure distribution in order to render said pressure distribution as optimum as possible. An assembly composed of various sheets is described in German Patent publication 3.7H.539- Said assembly provides an opaque sheet, located on the outside, to which an adhesive has been applied. A separating sheet is arranged adjoining said layer of adhesive. Carbon, which has been applied to a carrier, is present on the other side of said separating sheet. The separating sheet is removed in order to obtain an image on the outer sheet. As a result of the adhesive properties of the adhesive layer applied to the outer sheet, the carbon adheres to the outer sheet. The carrier provided with carbon can then likewise be removed and a transparent film applied over the adhesive layer. As a result, the pressure distribu¬ tion which is shown on the outer sheet can be observed. Such an assembly has the disadvantage that the pressure must be exerted on the side where the transparent sheet is applied. This pressure must propagate through a number of layers before it is transferred to the interface located betweenthe layer of adhesive and the carbon. This means that some of the sharpness of the image is lost. The aim of the present invention is to provide an assembly of the abovementioned type with which a greater contrast in coloration is obtained, so that it is possible to determine the pressures applied more accurately on the basis of the impression on the impression assembly. This aim is achieved with an impression sheet assembly described above in that the sheet located on the outside and provided with the adhes- ive layer is transparent and in that the carrier sheet is designed to receive an impression on the inside. The insight on which the invention is based is to apply the load to the transparent sheet and not to the opaque cover sheet. This was poss¬ ible only by providing the transparent sheet with an adhesive layer. With this arrangement it is no longer necessary for the carrier sheet to be transparent. By providing the carrier sheet with a grid pat¬ tern, a specific position can be accurately defined. The dye is preferably a combination of oils, lamp black, paraffin wax and graphite, which enters into a chemical reaction with the adhesive layer when pressure is exerted. A dye of this type is marketed by Lijnco, Groningen, under the name DLH <R '. Providing the dye-releasing layer with a protective sheet on the side facing towards the carrier sheet prevents an image already being formed on the carrier sheet during the first stage of transferring dye to the layer of adhesive. This would have an adverse effect on the subsequent result. The invention also relates to an impression assembly comprising an impression sheet as described above as well as a colour chart, the col¬ ouring of which corresponds to the colouring originating from the dye- releasing sheet. In this way it is easy to determine the level of the pres- sure at various points by comparing the colour chart and the impression. This is made even easier if the grid pattern described above is used. The invention also relates to a method for determining the pres¬ sure exerted on an impression sheet assembly as described above, wherein said method comprises the removal of the separating sheet, the placing of the remaining impression sheet assembly between the surfaces exerting pres¬ sure on one another, the transparent sheet facing towards the surface exerting the pressure to be determined, exertion of pressure, the removal of the impression assembly, the removal of the dye-releasing sheet, which optionally is provided with the protective sheet, and joining the transpar- ent sheet to the carrier sheet. The invention will be described in more detail below with the aid of an illustrative embodiment shown in the drawing. In the drawing: Fig. 1 shows a perspective view of the impression sheet assembly according to the invention; Fig. 2 shows the impression sheet assembly according to the invention when pressure is being exerted; Fig. 3 shows the impression sheet assembly according to the invention after removal of the dye-releasing component; and Fig. 4 shows a top view of the sheet according to Fig. 3 n combination with a calibration chart. In Fig. 1 a transparent sheet is indicated by 1. Said sheet is provided with an adhesive layer 2. A separating layer 3 is present to pre- vent contact with a following dye layer , which is applied to a protective sheet 5- A carrier sheet 6 is present as the bottommost layer. If an impression sheet assembly of this type has to be used to determine the pressure, separating sheet 3 is removed as shown in Fig. 2. By exerting pressure, for example with a foot 8, the adhesive layer 2 is brought into contact with the dye layer 4 and dye is combined with this adhesive layer 2. According to the invention, the protective sheet 5 is then removed, together with the dye still adhering thereto, and the assem¬ bly as shown, for example, in Fig. 3 is obtained. It can be seen from Fig. 4 that carrier sheet 6 is provided with a grid pattern ~ . This figure also shows the impression 9 of the foot con¬ cerned, which impression has various colour gradations. The pressure in each of the grid areas shown in Fig. 4 can be determined by using a colour chart 11 having a number of different colorations. It is particularly simple, for example, to cut an impression sheet assembly of this type to shape and to place it in a shoe. The person who is to use the shoe in future can then put his or her foot in the shoe and an image of the pressure distribution of the underside of the foot on the top of the insole is obtained. The supplier is able to make corrections on the basis of this image. The extent of the pressure can be qualified with the aid of the image obtained and the pressure can be qualified with the aid of, for example, a calibration chart. A non-limiting example of an impression sheet assembly according to the invention will be given below. The transparent sheet is composed of high-gloss cadmium-free plastic and has a thickness of 0.08 mm. The compressive strength is greater than 30 N/mm 2 (in the longitudinal and transverse direction in accordance with DIN 53355). The elongation at break according to DIN 53^55 is 200 % . The load carrying capacity is in the temperature range from -30°C to +70°C. The plastic is an antistatic material which, as far as is known, does not give rise to any allergic reactions on human skin. The adhesive layer 2 is composed of a removable acrylic emulsion in a layer thickness of 20 μ. The adhesive strength after 20 minutes is greater than 3 N/25 mm and after 24 hours is greater than 5 (FTMl on stain¬ less steel) . This adhesive is able to withstand the majority of oils and fats, weak acids and salts and mineral oils and no allergic reactions on human skin are known. The separating sheet was composed of glassine white and had a weight of about 62 g/m 2 and a thickness of about 55 U- The dye-releasing layer applied to protective sheet 5 was com¬ posed of modified DLA dye and weighed about 7 s/- ~2 - The colour was black and the dye was made up of graphite, oil, lamp black and paraffin wax. The addition of graphite and oil is important in this context. The protective sheet on which the dye-releasing layer described was located was composed of a sulphate-modified DLH and had a weight of 18 g/m 2 , a thickness of 0.03 mm and a natural colour. DLH (R) is a dye marketed by Lijnco, Groningen, The Netherlands. Finally, the carrier sheet 6 was composed of wood-free punch- card card board having a weight of 161 g/m 2 and a thickness of 0.170 mm in the colour white with a grid pattern applied thereon. It is, of course, possible to provide the carrier sheet with adhesive on the underside so that said sheet can, for example, be stuck inside a shoe as indicated above. These and other modifications are within the scope of the present Application as described in the appended claims.

Claims: Claims 1. Impression sheet assembly comprising, from one side, success¬ ively, at least a sheet (1) which is located on the outside and is provided with an adhesive layer (2), a separating sheet (3). a dye-releasing sheet (4) and a carrier sheet (6), characterised in that the sheet (1) located on the outside and provided with the adhesive layer (2) is transparent and in that the carrier sheet (6) is designed to receive an impression on the inside. 2. Impression sheet assembly according to Claim 1, wherein the dye comprises DLH <R) . 3. Impression sheet assembly according to Claim 1 or 2, wherein the carrier sheet (6) is not transparent. 4. Impression sheet assembly according to one of the preceding claims, wherein the carrier sheet (6) is provided with a grid pattern (7). 5- Impression sheet assembly according to one of the preceding claims, wherein the dye-releasing sheet (4) is provided, on the side facing towards the carrier sheet (6), with a protective sheet (5). 6. Impression assembly comprising an impression sheet assembly according to one of the preceding claims, as well as a colour chart (11), the colouring of which corresponds to the colouring originating from the dye-releasing sheet (4). 7. Method for determining the pressure exerted on an impression sheet assembly according to one of Claims 1-5. characterised in that said method comprises the removal of the separating sheet (3) , the placing of the remaining impression sheet assembly between the surfaces exerting pres¬ sure on one another, the transparent sheet (1) facing towards the surface exerting the pressure to be determined, exertion of pressure, the removal of the impression assembly, the removal of the dye-releasing sheet, which optionally is provided with the protective sheet, and joining the transpar- ent sheet to the carrier sheet. 8. Method according to Claim 7. wherein, after the transparent sheet has been applied to the carrier sheet, the coloration of the image produced is compared with calibration means. 9. Method according to Claim 8, wherein the determination is carried out by comparison with a colour chart.

Inventors: VISBEEN MARINUS ARTHUR, VISBEEN, MARINUS, ARTHUR
Applicants: MED GAIT TECH BV, VISBEEN MARINUS ARTHUR, MEDICAL GAIT TECHNOLOGY B.V., VISBEEN, MARINUS, ARTHUR
Application year: 1994
Main classification: A61B5
IPC codes: A61B5